Interleukin 20 (IL-20), a pleiotropic inflammatory cytokine, is a member of the IL-10 family, which includes IL-10, IL-19, IL-20, IL-22, IL-24, and IL-26. IL-20 is expressed in monocytes, epithelial cells, and endothelial cells. It acts on multiple types of cells via activating a heterodimer receptor complex of either IL-20R1/IL-20R2 or IL-22R1/IL-20R2. IL-20 has been found to be involved in various diseases, such as psoriasis, rheumatoid arthritis, atherosclerosis, ischemic stroke, osteoporosis, and renal failure. Certain anti-IL-20 antibodies have been reported to possess therapeutic effects in treating IL-20 associated diseases, e.g., osteoporosis and rheumatoid arthritis. U.S. Pat. Nos. 7,435,800, 7,611,705, 7,786,274, 7,837,994, 8,012,478; and US Patent Publications 20110305699 and 20090048432.
Monoclonal antibodies derived from non-human species are routinely used in biochemistry, molecular biology, and medical research. In addition, they are attractive therapeutic agents because of their high target specificity and effector functionality. However, one problem associated with the use of non-human antibodies as therapeutic agents is their immunogenicity, which substantially reduces the in vivo effectiveness of such antibodies. One approach to reduce immunogenicity is humanization, i.e., modifying non-human antibodies to increase their similarity to naturally-occurring human antibodies.